Are you using an Adj gas block?

[Bradpierson26]

I'll be using the 20" Faxon barrel from the group buy, rifle gas
Suppressed 75% of the time or so with either a sandman-S or a Recce 7.

To be honest it will mostly see wolf steel cased, occasionally some match ammo when I stretch to the steel at 1040 at my local range.

Is an adjustable gas block necessary? Otherwise I'll use a Geissele super gas block.
This is my first foray into 6.5g so I'd like to get it right, off the bat

[A5BLASTER]

From what I have read on hear from guys posting is most say you should use adjustable gas when shooting suppressed.

Take it for what it is I don't use a can so I don't have first hand knowledge of this but it's what has been posted here several times.

[SDet]

6.5 grendel, odin works 18" barrel, h3 buffer, thunder Beast ultra 7. Personally, this barrel is way over gassed, without the adjustable gas block, it will go maybe 2 rounds without jamming. With it, I'm averaging 50 rounds between jams, not great, but usable. I'll either play with the buffer more or rebarrel. For comparison, I've seen an Alexander arms upper go from no can through a 6.5mm ultra 9 without a hiccup.

Most ars are over gassed (can help with reliability with cheap ammo) and can benefit from an adjustable block even without a can. An adjustable gas block will also help reduce ejection port noise, giving you the most of your can.

[keystone183]

I see little to no reason NOT to run an adjustable block. To me, it lets you run a variety of ammo suppressed or not, and optimize each variation,with a small quick adjustment. No fuss.

Personally, I have had great experience with SLR, as a product and with customer service.

[TKO]

Adjustable gas block installation yields the maximum in versatility.

[82HALO]

+1 using SLR adjust blocks, they rock!

[LRRPF52]

I see little to no reason NOT to run an adjustable block. To me, it lets you run a variety of ammo suppressed or not, and optimize each variation,with a small quick adjustment. No fuss.

Personally, I have had great experience with SLR, as a product and with customer service.

The main reason not to use adjustable gas if you don't need it is port erosion.

You just took an open port and put a choke over it, turning it into a combustion chamber rather than the outlet for a manifold. There are ways to counteract that with nitriding and other processes, but I personally don't use Adjustable Gas if I don't need it.

[Klem]

The main reason not to use adjustable gas if you don't need it is port erosion.

You just took an open port and put a choke over it, turning it into a combination chamber rather than the outlet for a manifold. There are ways to counteract that with nitriding and other processes, but I personally don't use Adjustable Gas if I don't need it.

Interesting, but I am wondering how an adjustable block damages the barrel to the extent it is an issue.

The gas port is a certain dimension and we put a partial choke on that...How does that cause damage to anything? If you are suggesting the port will now be widened how does that affect anything given the block is still sealing the port, and the adjustable gas is still delivering gas at the rate dictated by the user.

Surely the gas block will also be eroded along with the barrel if that were the case.

Are there any cases of adjustable gas block damaging the barrel to the extent it needs changing sooner than otherwise? Or accuracy suffers?

[keystone183]

The main reason not to use adjustable gas if you don't need it is port erosion.

You just took an open port and put a choke over it, turning it into a combination chamber rather than the outlet for a manifold. There are ways to counteract that with nitriding and other processes, but I personally don't use Adjustable Gas if I don't need it.

I am also curious regarding the physics here. Not saying it isn't a thing, just can't wrap my mind around the how. Also, what kind of accelerated erosion are we talking here? If my port starts at. 07,how many regulated rounds(roughly) before I'm at. 09? . 1?

[LRRPF52]

The best way to approach adjustable gas is away from the port, like Savage did with the MSR-10 using a cylinder in the block, as opposed to a set screw over the port.

The problem with choking the port and increased erosion is that you end up chasing your port erosion with more choke, especially on softer steels like many stainless barrels are made from.

Since Grendel has such low working pressure from the start, I doubt you'll see rapid erosion on RLGS, but on MLGS and CLGS, it will happen faster, especially if the port is too large from the start.

Another problem with adjustable gas is carbon-welding, which has been really problematic for me using the set screw designs.

It would be interesting to do a length borescope analysis series of checks over a long round count, looking at port erosion between 2 different barrels of the same make, one choked, the other not.

[85_Ranger4x4]

Never thought about that angle but it makes a ton of sense. Just barely put your finger over your garden hose and there isn't much there, about choke it off and pressure increases and there is much more resistance at your finger.

I have never used an adjustable gas block and don't really plan to at this point. Nothing against them but I haven't felt that I needed one.

[keystone183]

The best way to approach adjustable gas is away from the port, like Savage did with the MSR-10 using a cylinder in the block, as opposed to a set screw over the port.

The problem with choking the port and increased erosion is that you end up chasing your port erosion with more choke, especially on softer steels like many stainless barrels are made from.

Since Grendel has such low working pressure from the start, I doubt you'll see rapid erosion on RLGS, but on MLGS and CLGS, it will happen faster, especially if the port is too large from the start.

Another problem with adjustable gas is carbon-welding, which has been really problematic for me using the set screw designs.

It would be interesting to do a length borescope analysis series of checks over a long round count, looking at port erosion between 2 different barrels of the same make, one choked, the other not.

Still not clear on the forces that are causing increased erosion when you have an adjustable block? Do you get faster erosion if you have a smaller dia gas port, all other factors of a barrel being equal?

Agree that the borescope analysis would be interesting, to put some hard data to it. I suspect that 99% of users never see this issue. I wonder if the useful life of the barrel might go before it became an issue.

As for carbon welding, i had at least 1000 rounds (more, but i can't guess at how many) through an SLR and when i swapped barrels a few months ago.....not even a smidge of resistance.... Excellent product.

[Klem]

The best way to approach adjustable gas is away from the port, like Savage did with the MSR-10 using a cylinder in the block, as opposed to a set screw over the port.

The problem with choking the port and increased erosion is that you end up chasing your port erosion with more choke, especially on softer steels like many stainless barrels are made from.

Since Grendel has such low working pressure from the start, I doubt you'll see rapid erosion on RLGS, but on MLGS and CLGS, it will happen faster, especially if the port is too large from the start.

Another problem with adjustable gas is carbon-welding, which has been really problematic for me using the set screw designs.

It would be interesting to do a length borescope analysis series of checks over a long round count, looking at port erosion between 2 different barrels of the same make, one choked, the other not.

With respect, until there is some hard evidence that either accuracy or barrel life suffers to a greater extent when using adjustable gas blocks then I don't think you can make such a claim. Certainly not with such matter-of-fact authority. Linking port erosion to adjustable gas blocks and then advising that non-adjustable is better than adjustable blocks is a non-sequitur.

I am with Keystone on this one. I have used SLR adjustable blocks in 5.56 and 6.5 uppers. They have all performed flawlessly. I agree however that the newer clamping-style blocks are an inherently better design than the older set screws.

Adjustable gas blocks are not essential for a suppressed AR, but they do help tame the increase in port pressure. This is evidenced by the brass ejection pattern.

[Drillboss]

I love all of y'all, but are you possibly talking past each other? I don't have first hand experience with suppressors, but from what I've read, adjustable gas is the way to go with them. I've put together 4 Grendel uppers without adjustable gas (and without suppressors) and they've all ran fine. A properly sized gas port seems to do the trick without suppression.

[keystone183]

I love all of y'all, but are you possibly talking past each other? I don't have first hand experience with suppressors, but from what I've read, adjustable gas is the way to go with them. I've put together 4 Grendel uppers without adjustable gas (and without suppressors) and they've all ran fine. A properly sized gas port seems to do the trick without suppression.

I don't think I'm talking past anyone? I'm genuinely curious as to the mechanism? causing increase erosion on an adjustable block. I do have two ars setup with nonadjustable blocks because I realize they add an obvious layer of complexity/potential failure. I just see that as an issue in the most extreme of cases.

[LRRPF52]

With respect, until there is some hard evidence that either accuracy or barrel life suffers to a greater extent when using adjustable gas blocks then I don't think you can make such a claim. Certainly not with such matter-of-fact authority. Linking port erosion to adjustable gas blocks and then advising that non-adjustable is better than adjustable blocks is a non-sequitur.

I am with Keystone on this one. I have used SLR adjustable blocks in 5.56 and 6.5 uppers. They have all performed flawlessly. I agree however that the newer clamping-style blocks are an inherently better design than the older set screws.

Adjustable gas blocks are not essential for a suppressed AR, but they do help tame the increase in port pressure. This is evidenced by the brass ejection pattern.

I never thought about it until Bill A. mentioned it, based on decades of engineer-level analysis and a 1-2 hour conversation on some of what he's seen with various adjustable gas designs, from the FAL to regulators on machine guns.

Seemed odd to me at first, but then again, every time I doubted him on something, I was wrong in the end, learned the hard way on my own.

He used a lot of his experiences when designing the Ulfberht gas system, as carbon welding is an inevitable that has to be deal with eventually. He said the FAL (L1A1) gas would carbon weld as well, and they had to repair them at that level in MoD.

Adjustable gas systems control how much gas flow there is through the port. When you constrain the flow, it leads to increased erosion. Smaller ports experience less erosion because there is less surface area for the expanding gases to impact and change direction through. It's why LMT uses angled gas ports on the MRP and MWS barrels, like the old AK gas port (only AK gas ports are monstrous in size).

[montana]

I'm going to have to agree with Klem on this subject. All of my Grendels and most of my 5.56 rifles have adjustable gas blocks. My 18" AA barrel needed the adjustable gas block since it came way over gassed and would not function with out it. The only effect with the increase port erosion, "if there is any" would be in accuracy and I doubt there would be enough compared to the life of the barrel in the first place to be concerned with . I too would like to see some hard evidence since my experience has shown differently. I have not had any problems with carbon welding since I clean and move my adjustment screw periodically. The new AK's have switched to the 90 degree port since they had problems with bullet jacket shearing with the 45 degree port. In any case having the ability to adjust my gas for my loads has out weighed any theory based problem with port erosion.

[Klem]

I love all of y'all, but are you possibly talking past each other? I don't have first hand experience with suppressors, but from what I've read, adjustable gas is the way to go with them. I've put together 4 Grendel uppers without adjustable gas (and without suppressors) and they've all ran fine. A properly sized gas port seems to do the trick without suppression.

Drillboss... We are talking about adjustable gas blocks vis-à-vis suppressors. I am saying they are not essential, but they help. As I understand 52 he is advocating not using them regardless because of increased port erosion. I am saying that is pretty damning advice given their prevalence in the market. So it's the old case of requesting justification...and I am still unconvinced.

I have used both regulated and unregulated blocks with suppressors and have done for a while now. They both work, however regulated gas makes an automatic system more user-friendly. The caveat is the Blackout which is under-gassed as a calibre to start with, so if you want to shoot subsonic 300BLK reliably then you need the port fully open. A fully-open regulated gas block in that case is just a waste.

I was originally issued with the SLR L1A1 (licensed equivalent of the FAL L1A1) in our military. I have never heard of carbon welding in the L1A1. They get carbon stains on the gas parts just like other gas guns but never did any parts 'weld' together.

I think port erosion is a non-issue in the choice between adjustable and non-adjustable gas for an AR. My concern about adjustable is similar to Keystone's however in that when you add moving parts to a system it increases the risk of failure. So far the only issue I have had was the choke screw on a new block out of the box would not move/stuck so Todd at SLR replaced it immediately.

[2_speed]

What do Y'all think about "bleed-off" gas blocks such as the Superlative Arms?

https://www.rainierarms.com/superlative-...-bleed-off

I bought one but haven't tried it out yet. (Sounds like a heck of a theory.)

Tom

[Klem]

What do Y'all think about "bleed-off" gas blocks such as the Superlative Arms?

https://www.rainierarms.com/superlative-...-bleed-off

I bought one but haven't tried it out yet. (Sounds like a heck of a theory.)

Tom

Looks like it is a similar principle to the gas system on the FAL L1A1 (mentioned above).


If that vented gas is not performing work; either pushing the bullet, or the BCG then it is being wasted to the atmosphere. If this vented gas does not drop the muzzle velocity significantly then I guess it's no big deal. But, it needs to be of some tangible benefit over existing designs to justify venting gas.